Scientists Unravel the Daily Cycles of Ocean's Most Abundant Organisms: Bacteria

What are the ocean's most abundant organisms? They're bacteria, of course. Now, scientists have learned a bit more about these tiny organisms. It turns out that communities of these ocean-dwelling microbes have their own daily cycles, just like the residents of a bustling city.

In order to learn a bit more about these bacteria, the researchers examined bacteria at a deep ocean study site near Hawaii. There, they observed different species of free-living, heterotrophic bacteria turning on diel cycling genes at slightly different times. This suggested that there was a wave of transcriptional activity that passed through the microbial community each day. More specifically, the scientists used advanced microbial community RNA sequencing techniques. This allowed them to conduct whole-genome profiling of multiple species at the same time.

"I like to say they are singing in harmony," said Edward F. DeLong, one of the researchers who made this discovery, in a news release. "For any given species, the gene transcripts for specific metabolic pathways turn on at the same time each day, which suggests a sort of temporal compartmentalization. It's a biologically and biogeochemically relevant new result."

What was most intriguing was that different species of bacteria expressed different types of genes in different, but consistent, cycles. For example, they would turn on the type of restorative genes needed to rebuild their solar-collecting traits and night while ramping up different gene activity to build new proteins during the day. This coordinated gene firing across different species could have important implications for energy transmission in the sea.

"There are some fundamental laws to be learned about how organisms interact, to make the system work better as a whole and be more efficient," said DeLong. "As its base, that's one of the main things we're after in SCOPE-these fundamental principles that make ecosystems work. These findings have tremendous applications in all sorts of arenas."

The findings are published in the journal Science.